Carbonproof plug



P 9 H. RABEZZANA 1,973,884

GARBONPROOF PLUG Filed Aug. 6, 1932 am ii; W9 Q 7 sorbing element 7,which as shown in the draw- 1 Prim d Sept. 1s, 1934 CARBONPROOF PLUGllector Rabeuana,

Flint, melt, Ym i.

none assignments, -to General Motors Como ration, Detroit, Mich, acorporation of-Delaian Application August 6, 1932, Serial No.- 627,684

' 4 Claims. (01. 123-169) This invention relates to ignition equipmentfor internal combustion engines, and'particularly to an improvement inspark plugs.

It is well recognized that the proper and elli- I cient functioning of aspark plug depends largely upon the temperature to which it is subjectedduring use. If a plug runs too.hot preignition troubles will result, andif it 'runs too cold, carbon or oil will deposit on the plug parts 10and, short-circuitthe gap. To avoid fouling, 'the temperature of thoseportions exposed in the combustion chamber must be high enough t bur-{naway any products of combustion deposited thereon and yet below thepoint where preignition is likely to occur. For this reason a plug mustbe designed according to the type of engine it is to be used with andthe temperature at which such-engine normally operates.

With these things in mindit is here proposed 20 to provide a spark plugespecially adapted for a. relatively cool running engine and which em-.

bodies a heat absorbingportion having a comparatively large surface areaexposed to the heat of combustion together with a restricted connectionwith the main body of the plug. Becauseof this arrangement, thedissipation or transference of heat taken upbythe heat absorbing portionwill be retarded and at a rate to store up sufficient-heat to maintainthe temperature high enough to burn away the carbon and keep the plugclean.

A better understanding of the invention will ,be vhad upon reference tothe accompanying drawing, wherein, Figure 1 is aside elevation' 35. of aspark plug in operative position,v in an engine cylinder head, a portionof the head beingshown in section. Figure 2 is a vertical sectional viewtaken on line 2-'2 of Figure 1, and Figure Figure 2."

Referring tothe drawing, the reference numeral 1 indicates-a watercooled cylinder head of an internal combustion engine, having acombustion chamber 2. Positioned within an openl threaded skirt 3 of theouter metal shell 4, which as is usual in spark plug design encloses aniiisulator core 5 surrounding a central electrode 6.

At the lower end'of the skirt and directly ex-- posed to' the combustionchamber 2 is a heat ab'- ing, may comprise a relatively narrow ringpresenting a large surface area to the heat, of com- 'bustion. This ringis connected to the main bodyof the-plug or skirt 3 by one or more re- 3is a transverse-section taken on line 3-3 of ing through the wall of thehead 1 is a screw strict/ed neck portions 8 which afford the only pathfor the flow of. heat absorbed by the ring 7 into the skirt 3, fromwhichthe heat is taken up by the head 1 and transferred to the coolingmedium in the water jacket. Because of the co restricted path ofheatflow and of the large surface area expos d to the heat, thetemperature of the narrow ring 7 will be maintained at a considerablyhigher point than that of the remainder of the plug and thereby preventthe 5 accumulation of carbon deposits.

."In the manufacture of the plug, thering 7.

may be formed initially as a part of theskirt proper and laterseparatedby a pair of saw kerfs cut inwardly from diametrically opposite pointsadjacent the inner end of the skirt.

To provide the spark gap, use is made of a side wire or groundedelectrode 9 ending. in

.spaced relation to the central electrode 6, and

mounted on the underside of the ring 7, prefer ably in line with one .ofthe neck portions 8. By so mounting the sidewire, the heat taken up byit can be readily transferred through the neck and into the main .wallof. the skirt, so as to obviate harmful effects of too much' heat on 80,the side wire.- 7 I It will be understood that by varying the size dfthe heat absorbing element and its connection and relation to the 'mainportion of the plug, the operating temperature thereof may be regulatedin accordance with conditions of use. It will also be understood thatvarious modifications may be made of the specific embodiment herereferred to. 7 I claim: 1. A spark plug. shell having a pair -of sawkerfs cut therein adjacent its inner end from diametrically oppositepoints and extending throughout the major portion of the shell to affordair space insulation between the end por-,

tion and the shell with restricted neck portions therebetween, and a'grounded electrode wire mounted -on said end portion in alinement withone of said neck portions. I

2. A spark plug shell having a pair of trans- .100

verse saw kerfs cut from opposite sides thereof i immediately adjacentits inner end to aiford a narrow heat storing ring in axial alinementand integral with the main body of the shell, said saw kerfs being so'related as to leave a bridge jacent itslinner end a saw kerf cut llO,

therebetween a restrictedf shell axis and immediately adjacent the innerend thereof to afford an opening through the wall thereof throughout amajor part of its circumferential extent for breaking the heat flow pathbetween the endmost portion and the main body of the shell.

H. RABEZZANA.

